Sep 12, 2023

Understanding Servo Motors

Servo motors are an integral part of closed-loop systems, comprising a control system, amplifier, servo motor, and encoder/resolver. These motors excel in providing efficient and precise motion within machines. A servo motor is essentially an electric motor with the added capability of high-precision control through sensors, enabling it to regulate linear or rotational speed and position accurately. In essence, a servo is a device that converts commands into motion, effectively controlling the direction and speed of this motion based on feedback.

The concept of the servo motor dates back to 1859 when Joseph Facort used it to control a ship's rudders using steam. In today's world, servo motors play crucial roles in various products and devices, from computers and gaming consoles with DVD players to modern vehicles, where they regulate throttle based on gas pedal input. Moreover, servo motors find extensive applications in aircraft, robotics, and industrial automation.

Types of Servo Motors

Servo motors come in various types, each suited for specific applications. The primary categories include AC servo motors, DC servo motors, positional rotation servo motors, continuous rotation servo motors, and linear servo motors. The key distinguishing factor for electric motors, including servo motors, is the type of current they use—either AC or DC.

DC Servo Motor

DC servo motors, as the name suggests, run on direct current (DC). They are essentially DC motors enhanced with sensors and encoders, providing feedback and enabling closed-loop control. DC servos are well-suited for smaller applications due to their versatility and precision. They find extensive use in robotics, automation, and CNC machinery. DC servo motors can further be categorized as brushed or brushless. Brushed DC motors employ mechanical commutation, while brushless DC motors utilize electronic commutation through sensors. Brushless DC motors are preferable for servo applications due to their superior efficiency and reliability.

AC Servo Motor

AC servo motors operate on alternating current (AC) and consist of an encoder and controller to facilitate control and feedback in a closed-loop system. These motors excel in high-precision applications and can generate significant torque by utilizing higher voltages. AC servo motors are generally more expensive but offer higher efficiency and greater capacity to handle current surges compared to DC servos.

Two primary types of AC motors include synchronous and asynchronous. Synchronous servo motors have rotor and stator speeds in sync, while asynchronous motors have a speed difference, creating slip and enabling higher torque. Synchronous servo motors find applications in power stations and manufacturing, while asynchronous servo motors are used in various applications, such as centrifugal fans, compressors, conveyors, and lifts.

Motion Characteristics

Servo motors exhibit distinct motion characteristics, including positional rotation servo motors, continuous rotation servo motors, and linear servo motors. Positional rotation servo motors rotate their output shaft by 180 degrees, with physical stops preventing further rotation. These motors are common in robotics, vehicles, and aircraft. Continuous rotation servo motors, similar to positional ones, can rotate in any direction, and their controllers manage both speed and direction. These motors are suitable for applications like radar dishes.

Linear servo motors convert circular motion into linear motion through additional gears. They are used in various applications, including modern airplanes as actuators.

In summary, servo motors are specialized motors designed for precision, rapid-reversing, and precision-positioning applications. They operate efficiently even in challenging environments, making them essential components in machinery such as inspection equipment, machine tools, packaging machines, and pick-and-place systems.

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